1. Field of the Invention
The present invention relates to a packed battery unifying a plurality of battery cells housed in a case.
2. Description of the Prior Art
A packed battery which has a plurality of battery cells housed in a case and connected with their electrodes to terminal members exposed outside the case, has been used as an electric power source for a photo camera, a video camera, or the like. Such a packed battery includes a couple of column-shaped battery cells 62, 62 housed in parallel arrangement in an elliptically cylindrical case 61 as shown in FIGS. 1, 2, 3 and 4 and is disclosed in Japanese Patent Application Laid-Open No. 14662 (1987). Their respective positive electrodes 62a, 62a are arranged in opposite directions. The battery cells 62, 62 are connected in series by a connector 63 placed at one end so as to extend between the positive and negative electrodes. The two battery cells 62, 62 are also connected at the other end to terminal members 64, 64 respectively. Each of the two terminal members 64, 64 is exposed, at one end, outside of the case 61. The case 61 comprises a pair of half-units 61a, 61a so as to be separable lengthwisely thereof.
A method of assembly of such a packed battery is as follows. The two battery cells 62, 62 are housed in the half-units 61a, 61a with the connector 63 disposed at one end and the terminal members 64, 64 disposed at the other end. The case 61 is securely gripped at both top and bottom portions between an ultrasonic wave transducer and a fixing stand and then, exposed to ultrasonic wave. Accordingly, the half-units 61a, 61a are heated up along their confronting circumferential edges and welded together. However according to such an arrangement for welding, the case 61 has poor welding effect on both side portions thereof. More particularly, intensive welding about the side portions of the case 61 results in overheat at the top and bottom portions of the same. Thus, the finish of welding becomes unsatisfactory and the accuracy in the exterior measurements cannot be secured. This occurs due to less energy transfer of ultrasonic wave vibration to the side welding portions of the case half-units 61a, 61a.
There are also other similar arrangements of a packed battery described in U.S. patent application No. 899036 (1978) and U.S. patent application No. 425055 (1973), each of which has a lengthwisely separable battery case thus offering a similar welding problem.
FIG. 5 shows a packed battery disclosed in Japanese Patent Application Laid-Open No. 39862 (1986) having a bottom closed cylindrical case 71 which contains a couple of battery cells 72, 72 arranged in opposite directions to each other and is closed at upper end with a lid 73. The lid 73 has on the inner side a connector 74 for connection in series. The case 71 has in the bottom a pair of openings 75, 75 for access to their respective positive and negative electrodes of the two battery cells 72, 72. Although the case 71 and the lid 73 are easily and securely joined to each other by welding, in this arrangement, both the positive and negative electrodes sink into the case 71 thus limiting effective use and being less practical for use.
As for the positions of electrodes or terminal members, it is desirable to have the terminal members 64, 64 extending between the end and side of the case as shown in FIGS. 1 to 4. Such an arrangement allows an electric apparatus using a packed battery to locate its power terminals more flexibly. In other words, the power terminals of the apparatus can be located on either an end side or a peripheral side of the apparatus. On the other hand, in U.S. patent application Nos. 899036 (1978) and 425055 (1973), the power terminals are provided only on an end side.
A packed battery is most commonly used in a photo camera. Such specific packed batteries are disclosed in Japanese Patent Application Laid-Open Nos. 2157, 2158 and 2159 (1987) having power terminals on both end and peripheral sides of the case although their case constructions are not clearly described.